This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 101 23 282.9, filed on May 12, 2001, the entire disclosure of which is incorporated herein by reference.
The invention relates to a pyrotechnic igniter arrangement with an integrated electronic assembly, especially for triggering passenger or occupant protection devices in motor vehicles, for example. The igniter arrangement includes a pyrotechnic zone for a pyrotechnic charge or active mass and an electrically ignitable ignition bridge, as well as an electronics zone for an electronic assembly, such as especially, the ignition electronics.
An igniter arrangement of the above mentioned general type is disclosed in German Patent DE 198 36 280 C1, for example. In that reference, a protective wall separates the pyrotechnic area or zone from the electronic area or zone. Furthermore, separate contact elements are provided in this protective wall, whereby these separate contact elements must be contacted on both sides of the wall, in order to connect the electronic assembly in the electronic zone with the ignition bridge in the pyrotechnic zone. A one-piece carrier arrangement or substrate cannot be used for both the ignition/pyrotechnic zone as well as the electronic zone, because of their physical separation by the protective wall.
German Patent Laying-Open Document DE 198 36 278 A1 discloses an igniter arrangement with a carrier arrangement or substrate for the ignition bridge as well as for the electronic assembly. The entire carrier arrangement is arranged in the ignition capsule with the pyrotechnic charge or active mass. However, the carrier arrangement is covered with a damping layer of shock absorbing material over a portion thereof, preferably at least in the area of the electronic assembly.
Another simple carrier arrangement or substrate, for example a circuit board, to be used as a supporting carrier for the entire ignition arrangement including the ignition bridge and the electronic assembly, is disclosed in published European Patent Application EP 0,555,651 B1, for example. Using such simple carrier arrangements is more economical than providing separate carrier arrangements for the pyrotechnic zone and for the electronic zone respectively. However, such simple carrier arrangements do not provide a comparably effective protection for the electronic assembly against the effects of pressure, temperature, or forces that arise during the triggering or ignition of the igniter arrangement.
This can be disadvantageous, if the pressure, temperature, forces, or other mechanical influences arising from the pyrotechnic zone in turn are transmitted to the electronic assembly and lead to a disruption thereof. Namely, the igniter arrangement is typically connected via its electronic assembly to a databus, which in turn is further connected to a central unit and other igniter arrangements, for example in an ignition bus for occupant protection devices in a motor vehicle. It is desired that an igniter arrangement should remain at least partially functional after its ignition, for example to confirm the proper ignition or the like. In any event, the electronic assembly must remain intact or undisturbed to an extent sufficient to ensure that the further data exchange on the ignition bus will not be interrupted or interfered-with by the igniter arrangement that has been ignited.
In view of the above, it is an object of the invention to provide an igniter arrangement which may be easily and economically manufactured, and which ensures that the, electronic assembly remains largely functional, even after triggering or ignition of the igniter arrangement, at least so that a further data transmission on the connected bus system will not be hindered or interfered with. Particularly, it is an object of the invention to protect the electronic assembly in the electronic zone from the mechanical influences, and especially the mechanical forces, arising in the pyrotechnic zone of the igniter assembly during ignition thereof. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved in a pyrotechnic igniter arrangement with an integrated electronic assembly, according to the invention, wherein the pyrotechnic igniter arrangement includes a pyrotechnic area or zone, an electronic area or zone, a supporting carrier arrangement or substrate that extends between and into both the pyrotechnic zone and the electronic zone, a pyrotechnic charge or active mass and an electrically ignitable ignition bridge arranged in the pyrotechnic zone, and an electronic assembly arranged in the electronic zone. The electronic assembly is arranged on and electrically connected with the carrier arrangement in the electronic zone, while the ignition bridge is arranged on and electrically connected with the carrier arrangement in the pyrotechnic zone. The carrier arrangement has a parting or decoupling feature at a parting or decoupling location, for mechanically decoupling a first portion of the carrier arrangement located in the pyrotechnic zone from a second portion of the carrier arrangement located in the electronic zone. The parting or decoupling feature may comprise a frangible link or intended breaking area, or an elastically flexible and bendable area, of which the strength or stiffness has been reduced in comparison to the remainder of the carrier arrangement, so that this parting or decoupling feature will break or elastically yield in the event that mechanical loads applied thereto exceed a prescribed maximum load threshold. Thus, forces or mechanical loads or thermal loads exceeding the prescribed maximum load threshold will not be transmitted or coupled from the first portion of the carrier arrangement in the pyrotechnic zone to the second portion of the carrier arrangement in the electronic zone.
The basic idea of the invention is to provide a decoupling location or feature for mechanically decoupling the portion of the carrier arrangement located in the pyrotechnic zone from the rest of the carrier arrangement. This is achieved, as mentioned above, by reducing the strength or stiffness of the carrier arrangement in this decoupling location, so that the decoupling location will break, yield or flex in the event of a mechanical load exceeding a prescribed maximum load threshold being applied thereto. The decoupling location can, for example, be embodied as a frangible link feature, i.e. an intended breaking location, or as an intended flexing or bending location, or as a meltable soldered connection.
With the inventive features, it is not necessary to avoid the structural separation of the electronic zone and the pyrotechnic zone, for example by a protective wall therebetween, yet the invention still provides a simple carrier arrangement in common for the electronic assembly in the electronic zone as well as for the ignition bridge in the pyrotechnic zone. In a particular embodiment, the ignition bridge extends through a protective wall provided between the electronic zone and the ignition zone. The carrier arrangement is simply provided with one or more decoupling locations, which mechanically decouple the portion of the carrier arrangement located in the electronic zone from the portion located in the pyrotechnic zone, after ignition of the pyrotechnic charge or active mass, i.e. after the actual ignition pulse has been applied to the ignition bridge, yet preferably during the burning of the pyrotechnic charge. Thereby, the mechanical decoupling feature at the decoupling location prevents the further transmission of mechanical loads exceeding the prescribed acceptable load threshold level from the pyrotechnic zone to the electronic zone.
According to a preferred further embodiment feature, the portion of the carrier arrangement in the pyrotechnic zone is preferably at least partially surrounded by a sheath or encasement of a pressure absorbing first material, and furthermore, the portion of the carrier arrangement in the electronic zone is preferably at least partially, but preferably completely, enclosed or encased with a second material that is harder than the softer pressure absorbing first material in the pyrotechnic zone. Preferably, the protective wall and the encasing of the carrier arrangement in the electronic zone are embodied in an integral one-piece manner of this harder second material.
In a further preferred embodiment, the parting or decoupling feature or features, and/or the encasing of the carrier arrangement in the pyrotechnic zone, are dimensioned and embodied so that they will be separated for decoupling the two portions of the carrier arrangement only when an applied thermal and/or mechanical load in the pyrotechnic zone or on the carrier arrangement exceeds a prescribed thermal and/or mechanical load threshold during the burning of the pyrotechnic charge.